Transformer having magnetic shields

ABSTRACT

Leakage flux shields for shell-form power transformers. One shield surrounds the upper portion of the transformer windings and another shield surrounds the lower portion of the transformer windings. Each shield includes a plurality of laminated magnetic bundles arranged to form closed magnetic paths around the transformer windings. Each of the joints between adjacent bundles in the flux paths are formed by bundle faces which contain an edge of each lamination in the bundle.

United States Patent 1 Moan 1 June 28, 197

[54-] TRANSFORMER HAVING MAGNETIC 3,464,041 8/1969 Waterman 336/84 x SELDS 3,534,311 10/1970 Bell 336/84 3,538,472 11/1970 Bell et al 336/84 [75] Inventor: Virgil L. Boaz, Dalewille, Ind. [73] Assignee: Westinghouse Electric Corporation, Primary Examiner-Thomas KOZma Pittsburgh, P Attorney, Agent, or Firm-J. R. Hanway [22] Filed: Apr. 118, 1973 ABS CT [211 App! 352370 Leakage flux shields for shell-form power transformers. One shield surrounds the upper portion of the [52] US. Cl 336/84, 336/212, 336/214, transformer windings and another shield surrounds the 336/216 lower portion of the transformer windings. Each shield [51] lnt. Cl Holt 15/04, HOlf 27/24 n lud s a plurality of laminated magnetic bundles ar- [58] Field of Search 336/84, 212, 214, 215, r ng t form closed magnetic paths around the 336/234, 216, 217 transformer windings. Each of the joints between adjacent bundles in the flux paths are formed by bundle [56] Referen Cit d faces which contain an edge of each lamination in the UNITED STATES PATENTS 1/1944 Sauer 336/84 bundle.

7 Claims, 5 Drawing Figures PATENTEUmza lam SHEH i W BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates, in general, to electrical inductive apparatus and, more specifically, to transformers having magnetic shields.

2. Description of the Prior Art Various arrangements have been used to shield the transformer enclosure, the core support beams, and other metallic parts from the effects of leakage flux which surrounds the exposed portions of shell-form transformer windings. One of the most useful methods involves attaching bundles of laminations to the transformer-enclosure. The leakage flux entersthese bundles and some of the flux is directed back into the magnetic core. U.S. Pat. Nos. 3,160,839, 3,534,311 and 3,538,472, which are all assigned to the assignee of this invention, show and describe various shielding arrangements which are useful in reducing the effects of the leakage flux. I

The arrangements of bundles known in the prior art have not provided a reasonably low reluctance mag netic path for the leakage flux. In some arrangements, the joints between adjacent bundles'are made in such a manner that flux crossing the joints enters a bundle through the flat side of a lamination. This type of 1 joint increases the reluctance of the magnetic path. Therefore, it is desirable, and it is an object of this invention, to provide a leakage flux shield which provides a lowreluctance path for the leakage flux which is captured by the shield.

Many shielding arrangementsconstructed according tothe prior art do not provide a good magnetic path for the leakage flux captured by the shield to return to the magnetic core for the purpose of linking all of the transformer windings. In several prior art arrangements, the leakage flux enters the core mainly through the broad side of the core laminations. It is also desirable, and it is a further object of this invention, to provide a leakage flux shield which provides a lowreluctance return path to direct the captured leakage flux through the center of the windings of the transformer.

SUMMARY OF THE INVENTION There is disclosed herein new and useful arrangements for constructing leakage flux shields. shield for the. upper portion of shell-form transformer windings is constructed of laminated bundles positioned in such a manner that a closed magnetic path is provided around the windings. All of the bundles which form the path in the shield have joints therebetween which are defined by faces of the bundles which contain an edge of each bundle lamination. Each bundle is joined to an adjacent bundle by either its end or its laminated face. A closed low-reluctance flux path exists along the sides of the upper winding portions, along the ends of the upper winding portions, and through the center of the windings. A shield for the lower portion of the shell-form transformer windings is also constructed of laminated bundles positioned in such a manner that'a closed magnetic path is provided around the windings. Joints between the bundles are defined by either end or laminated faces of adjacent bundles. A closed lowreluctance magnetic path exists along the sides and bot- 2 tom of the lower winding portions, along the ends of the lower winding portions, and through the center of the windings. For construction convenience, the bun dles may be attached to the transformer enclosure which is disposed around the magnetic core and the windings.

BRIEF DESCRIPTION OF THE DRAWING Further advantages and uses of this invention will be come more apparent when considered in view of the following detailed description and drawing, in which:

FIG. I is a view of a shell-form transformer illustrating the core,.windings and enclosure members about which a leakage flux shield may be positioned;

FIG. 2 is a view of a leakage flux shield constructed according to this invention and suitable for placement around the upper portion of the windings of the transformer shown in FIG. 11;

FIG. 3 is a view of a shield lamination bundle illustrating nomenclature used in describing and claiming this invention;

FIG. 4 is a view of a leakage flux shield constructed according to this invention and suitable for placement around the lower portion of the windings of the transformer shown in FIG. 11; and

FIG. 5 is an elevational view, partly in section, of the transformer shown in FIG. 1 with the shields of FIGS. 2 and 4 positioned thereon.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Throughout the following description, similar reference characters refer to similar elements or members in all the figures of the drawing.

Referring now to the drawing, and to FIG. 1 in particular, there is shown a portion of a three-phase shellform power transformer. The laminated magnetic core includes a plurality of laminations, or punchings, which are stacked to provide the desired shape. The steel T-beams 112 and 14 extend through the core l0 to provide additional strength. Openings, or windows, in the magnetic core 10 contain the windings of the transformer, such as the phase windings 116, 18 and 20. Each of the windings 116, 18 and 20 normally contains primary and secondary windings having one or more coil disc sections. Other winding arrangements for single or three-phase applications may be used within the contemplation of this invention.

The windings 116, 118 and 2t) have upper portions 'which project from the core 10 generally above the portion 26 of the enclosure 22 generally encloses the lower portion of the windings 116, 118 and 20. A top porflux would enter the enclosure 22 and losses in the form of heat would occur.Enclosure shielding whichcap- 3 tures and directs the leakage flux back through the coils as shown generally by the line 25 would reduce the losses of the transformer.

FIG. 2 is a view of a shield 30 suitable for placement around the upper portion of the windings 16, 18 and 20. Winding 18 is shown therein to illustrate the placement of the shield with respect to the windings. The shield 30 intercepts the leakage flux before it reaches the enclosure 22 and directs the leakage flux back through the center of the windings. By diverting the leakage flux in this manner, the losses are reduced since the leakage flux is directed by a low-reluctance path through the windings to link all of the coil turns. The outer shielding bundles comprising the shield may be attached to the top portion of the enclosure 22, to a separate mounting frame positioned over the windings, or to any other structure which places the bundles in the proper position relative to each other and to the windings.

FIG. 3 is a view of a shielding bundle 28 similar to the shielding bundles from which the enclosure shield 30 is constructed. The bundle 28 contains a plurality of grain-oriented magnetic laminations, or punchings, which are stacked with their edges in alignment. The length dimension L is greater than the width dimension W" or the height dimension H. For the purposes of this specification, the faces of the bundles will be referred to as the side, end and laminated faces as shown in FIG. 3. This nomenclature also applies to the three sides of the bundle 28 which are not shown. The side faces are formed and defined by the outermost laminations of the bundle and do not contain any of the joints which exist between adjacent laminations. The end faces are formed by the ends of the laminations and contain an end of each lamination in the bundle. The laminated faces are formed by sides of the laminations and contain an edge of each lamination in the bundle. It is within the contemplation of this invention that a shielding bundle may have butt or stepped-type joints therein between laminations forming the ends of the bundle. This is necessary when it is impractical to provide single laminations having a length dimension as long as the desired length of the bundle.

Referring again to FIG. 2, the shield 30 is constructed from a plurality of'shielding bundles. The shielding current path along the points where the bundles would come in contact with each other. The gap may be suitably spaced by the use of a coating on the bundles, an insulating sheet placed in the joints, or by any other suitable method. Similar gaps exist in all of the other joints of this invention.

Shielding bundles 42, 44, 46, 48 and 50 are positioned substantially parallel and adjacent to each other with their laminated faces adjacent to the laminated faces of the bundles 52 and 54. Bundles 56 and 58 extend through the winding 18 with their end faces ad jacent to the laminated faces of the bundles 48 and 50, respectively. It is within the contemplation of this invention that suitable joints may be formed between adjacent bundle faces with a tongue and groove pattern. Bundles 60 and 62 are positioned at the other end of bundles 56 and 58 similar to bundles 48 and 50, all respectively. Bundles 64, 66, 68, 70, 72 and 74 are all positioned, with respect to each other, similar to the bundles 46, 44, 42, 40, 54 and 52, respectively. The remaining bundles of the shield 30 are denoted by primed reference numerals which indicate which of the shielding bundles previously described are similarly positioned on opposite sides of the center of the winding bundles are arranged to form a substantially closed magnetic path around the winding 18. In addition, the interfaces, or joints, between adjacent bundles are oriented so that flux traveling therethrough enters and leaves the bundles at an end or laminated face thereof. This arrangement allows the flux to penetrate the laminations in the direction which produces a minimum amount of losses.

The number of bundles positioned substantially parallel and adjacent to each other is dependent on the size of the bundles, the size of the winding, the amount of losses tolerable, and on other factors. It is within the contemplation of this invention that a different number of bundles may be used than the number of bundles illustrated in FIG. 2.

Leakage flux entering the bundles 32, 34, 36 and 38 is directed away from the enclosure which would be po- I sitioned around the shield 30. This flux links the winding 18 by traveling through bundle 40 to bundles 52 and 54, to bundles 48, 50, and 48, and to bundles 56, 58, 58' and 56'. The closed magnetic path is completed by one or more of the bundles 60', 62', 62, 60, 70, 72 and 74. Bundles 56, 58, 58' and 56 may be attached or secured to the beam 14 or the beam 14 may be laminated in a manner which will produce properly oriented joints at the ends of the beam 14.

FIG. 4 illustrates a shield 78 which is constructed for placement around the lower portion of the windings, with winding 18 partially illustrated in assembled relationship with the shield 78. Placement and orientation of the bundles 80 is similar to the corresponding bundles 32, 34, 36 and 38 described in connection with FIG. 2. Bundles 80 join the bundle 82 which joins with bundle 84. Flux in bundle 84 travels to bundles 86 and then to bundles 88. The magnetic path is closed by bundles 90, 92 and 94. A closed magnetic path around the other side of the winding 18 is provided by the addition of bundles 96, 98 and 100. The bottom bundles, such as bundle 102, substantially over the entire lower area of the windings, unlike the upper shield 30 which must provide space for passage of the winding leads. This reduces the leakage flux which may penetrate the shield 78 and enter the enclosure which is positioned around the transformer. Bundles 104, 106, 108 and 110 are positioned as illustrated to shield the ends of the enclosure from leakage flux.

FIG. 5 is an elevational view, partly in section, of a transformer having leakage flux shields disposed around the windings of the transformer. The relative position of the windings with respect to the shields 30 and 78 is shown by winding 18 which is illustrated in phantom. Insulating spacers 110 of wood or another suitable material are positioned between the shields 30 and 78 and the core 10 to allow for clearance of the beams 12 and 14. Insulating spacers 112 hold the core and winding assembly 24 firmly within the enclosure 22..

The various bundles of the shields 30 and 7% are attached to the enclosure 22 by a suitable method, such as by welding. Before assembly, the transformer enclosure22 usually comprises a top and bottom portion. The bundles of the shield 78 are attached to the lower portion before thecore is set in place. After the core has been set in place, the top portion of the enclosure 22, with the bundles of the shield 3t) attached thereto, is lowered over the core and coil assembly 24.. The bundles which project through the winding openings are placed therein at a convenient time during the construction of the core and winding assembly 2%.

The shields Bull and 78 which are provided by this arrangement permit minimum losses between bundle joints. Since numerous changes may be made in the above-described apparatus and since different embodiments of the invention may be made without departing from the spirit thereof, it is intended that all of the matter contained in the aforegoing description, or shown in the accompanying drawing, shall be interpreted as illustrative rather than limiting.

I claim as my invention:

1. Electrical inductive apparatus comprising:

a shell-form laminated magnetic core;

a plurality of windings disposed in inductive relationship with said core;

an enclosure disposed around said core and windings,

said enclosure having a top portion which surrounds an upper portion of said windings and a bottom portion which surrounds a lower portion of said windings; and

shielding bundles disposed around said windings,

each of said shielding bundles comprising a plurality of magnetic laminations stacked with their edges in alignment, with each of said shielding bundles having an end face formed by the ends of its laminations, a side face defined by one of its outermost laminations, and a laminated face which contains an edge of each of its laminations;

said shielding bundles being positioned to form a first substantially closed magnetic path around the outside of said windings, and a second substantially closed magnetic path around the, outside and through the center of said windings, with some of the shielding bundles in the first and second magnetic paths being positioned adjacent to each other to permit the transfer of flux between the first and second magnetic paths, with the faces of all the joints through which flux passes between adjacent shielding bundles in the same magnetic path and between adjacent shielding bundles of the first and second magnetic paths containing an edge of each lamination in the shielding bundle forming the face.

2. The electrical inductive apparatus of claim ll wherein:

a first of the shielding bundles is positioned at the side of the upper portion of the windings with its laminated face adjacent to the windings;

a second of said bundles is positioned with a face a fourth of said bundles is positioned with a face thereof adjacent to a face of the third bundle and with their side faces perpendicular to each other;

a fifth of said bundles is positioned with a face thereof adjacent to a face of the fourth bundle and with their laminated faces perpendicular to each other;

a sixth of said bundles is positioned with a face thereof adjacent to a face of the fifth bundle and with their laminated faces perpendicular to each other;

a seventh of said bundles is positioned with a face thereof adjacent to a face of the sixth bundle and with their side faces perpendicular to each other; and

an eighth of said bundles is positioned with a face thereof adjacent to a face of the seventh bundle and with their side faces perpendicular to each other, said eighth bundle also being positioned with a face thereof adjacent to a face of the first bundle and with their laminated faces perpendicular to each other.

3. The electrical inductive apparatus of claim 1 wherein:

a first of said bundles is positioned at the side of the upper portion of the windings with its laminated face adjacent to said windings;

a second of said bundles is positioned with a laminated face adjacent to an end face of said first bundle;

a third of said bundles is positioned with a laminated face adjacent to a laminated face of said second bundle;

a fourth of said bundles is positioned with a laminated face adjacent to said laminated face of said third bundle;

a fifth of said bundles is positioned with an end face adjacent to a laminated face of said fourth bundle;

a sixth of said bundles is positioned with a laminated face adjacent to an end face of said fifth bundle;

a seventh of said bundles is positioned with a laminated face adjacent to a laminated face of said sixth bundle; and I an eighth of said bundles is positioned with a laminated face adjacent to said laminated face of said seventh bundle, with a laminated face of said eighth bundle being positioned adjacent to an end face of said first bundle.

d. The electrical inductive apparatus of claim 1 wherein all of the joints are butt-type joints having a suitably small gap distance between the faces forming the joints.

5. The electrical inductive apparatus of claim ll wherein at least one of said joints is a tongue and groove type joint.

6. The electrical inductive apparatus of claim )1 wherein:

a first of said shielding bundles is positioned at the side of the lower portion of the windings with its laminated face adjacent to the windings;

a second of said bundles is positioned with a face .thereof adjacent to a face of the first bundle and with their laminated faces perpendicular to each other;

a third of said bundles is positioned with a face thereof adjacent to a face of the second bundle and 7 with their side faces perpendicular to each other;

a fourth of said bundles is positioned with a face thereof adjacent to said face of the third bundle and with their side faces perpendicular to each other;

a fifth of said bundles is positioned with a face thereof adjacent to a face of the fourth bundle and near one end of said fourth bundle with their laminated faces perpendicular to each other;

a sixth of said bundles is positioned with a face thereof adjacent to a face of the fourth bundle and near the other end of said fourth bundle with their laminated faces perpendicular to each other;

a seventh of said bundles is positioned with a face thereof adjacent to a face of the fifth and sixth bundles and with their laminated faces perpendicular to each other;

an eighth of said bundles is positioned with a face thereof adjacent to a face of the seventh bundle and with their side faces perpendicular to each other; and i a ninth. of said bundles is positioned with a face thereof adjacent to said face of the eighth bundle and with their side faces perpendicular to each other, with said ninth bundle being positioned with a face thereof adjacent to a face of the first bundle and with their laminated faces perpendicular to each other. 7. The electrical inductive apparatus of claim 1 wherein:

a first of said bundles is positioned at the side of the lower portion of the windings with its laminated face adjacent to said windings;

a second of said bundles is positioned with a laminated face adjacent to an end face of said first bundle;

a third of said bundles is positioned with a laminated face adjacent to a laminated face of said second bundle;

a fourth of said bundles is positioned with a laminated face adjacent to said laminated face of said third bundle;

a fifth of said bundles is positioned with an end face adjacent to one end of a laminated face of said fourth bundle;

a sixth of said bundles is positioned with an end face adjacent to the other end of the laminated face of said fourth bundle;

a seventh of said bundles is positioned with a laminated face adjacent to an end face of said fifth and sixth bundles;

an eighth of said bundles is positioned with a laminated face adjacent to a laminated face of said seventh bundle; and

a ninth of said bundles is positioned with a laminated face adjacent to said laminated face of said eighth bundle, with a laminated face of said ninth bundle being positioned adjacent to an end face of said 

1. Electrical inductive apparatus comprising: a shell-form laminated magnetic core; a plurality of windings disposed in inductive relationship with said core; an enclosure disposed around said core and windings, said enclosure having a top portion which surrounds an upper portion of said windings and a bottom portion which surrounds a lower portion of said windings; and shielding bundles disposed around said windings, each of said shielding bundles comprising a plurality of magnetic laminations stacked with their edges in alignment, with each of said shielding bundles having an end face formed by the ends of its laminations, a side face defined by one of its outermost laminations, and a laminated face which contains an edge of each of its laminations; said shielding bundles being positioned to form a first substantially closed magnetic path around the outside of said windings, and a second substantially closed magnetic path around the outside and through the center of said windings, with some of the shielding bundles in the first and second magnetic paths being positioned adjacent to each other to permit the transfer of flux between the first and second magnetic paths, with the faces of all the joints through which flux passes between adjacent shielding bundles in the same magnetic path and between adjacent shielding bundles of the first and second magnetic paths containing an edge of each lamination in the shielding bundle forming the face.
 2. The electrical inductive apparatus of claim 1 wherein: a first of the shielding bundles is positioned at the side of the upper portion of the windings with its laminated face adjacent to the windings; a second of said bundles is positioned with a face thereof adjacent to a face of the first bundle and with their laminated faces perpendicular to each other; a third of said bundles is positioned with a face thereof adjacent to a face of the second bundle and with their side faces perpendicular to each other; a fourth of said bundles is positioned with a face thereof adjacent to a face of the third bundle and with their side faces perpendicular to each other; a fifth of said bundles is positioned with a face thereof adjacent to a face of the fourth bundle and with their laminated faces perpendicular to each other; a sixth of said bundles is positioned with a face thereof adjacent to a face of the fifth bundle and with their laminated faces perpendicular to each other; a seventh of said bundles is positioned with a face thereof adjacent to a face of the sixth bundle and with their side faces perpendicular to each other; and an eighth of said bundles is positioned with a face thereof adjacent to a face of the seventh bundle and with their side faces perpendicular to each other, said eighth bundle also being positioned with a face thereof adjacent to a face of the first bundle and with their laminated faces perpendicular to each other.
 3. The electrical inductive apparatus of claim 1 wherein: a first of said bundles is positioned at the side of the upper portion of the windings with its laminated face adjacent to said windings; a second of said bundles is positioned with a laminated face adjacent to an end face of said first bundle; a third of said bundles is positioned with a laminated face adjacent to a laminated face of said second bundle; a fourth of said bundles is positioned with a laminated face adjacent to said laminated face of said third bundle; a fifth of said bundles is positioned with an end face adjacent to a laminated face of said fourth bundle; a sixth of said bundles is positioned with a laminated face adjacent to an end face of said fifth bundle; a seventh of said bundles is positioned with a laminated face adjacent to a laminated face of said sixth bundle; and an eighth of said bundles is positioned with a laminated face adjacent to said laminated face of said seventh bundle, with a laminated face of said eighth bundle being positioned adjacent to an end face of said first bundle.
 4. The electrical inductive apparatus of claim 1 wherein all of the joints are butt-type joints having a suitably small gap distance between the faces forming the joints.
 5. The electrical inductive apparatus of claim 1 wherein at least one of said joints is a tongue and groove type joint.
 6. The electrical inductive apparatus of claim 1 wherein: a first of said shielding bundleS is positioned at the side of the lower portion of the windings with its laminated face adjacent to the windings; a second of said bundles is positioned with a face thereof adjacent to a face of the first bundle and with their laminated faces perpendicular to each other; a third of said bundles is positioned with a face thereof adjacent to a face of the second bundle and with their side faces perpendicular to each other; a fourth of said bundles is positioned with a face thereof adjacent to said face of the third bundle and with their side faces perpendicular to each other; a fifth of said bundles is positioned with a face thereof adjacent to a face of the fourth bundle and near one end of said fourth bundle with their laminated faces perpendicular to each other; a sixth of said bundles is positioned with a face thereof adjacent to a face of the fourth bundle and near the other end of said fourth bundle with their laminated faces perpendicular to each other; a seventh of said bundles is positioned with a face thereof adjacent to a face of the fifth and sixth bundles and with their laminated faces perpendicular to each other; an eighth of said bundles is positioned with a face thereof adjacent to a face of the seventh bundle and with their side faces perpendicular to each other; and a ninth of said bundles is positioned with a face thereof adjacent to said face of the eighth bundle and with their side faces perpendicular to each other, with said ninth bundle being positioned with a face thereof adjacent to a face of the first bundle and with their laminated faces perpendicular to each other.
 7. The electrical inductive apparatus of claim 1 wherein: a first of said bundles is positioned at the side of the lower portion of the windings with its laminated face adjacent to said windings; a second of said bundles is positioned with a laminated face adjacent to an end face of said first bundle; a third of said bundles is positioned with a laminated face adjacent to a laminated face of said second bundle; a fourth of said bundles is positioned with a laminated face adjacent to said laminated face of said third bundle; a fifth of said bundles is positioned with an end face adjacent to one end of a laminated face of said fourth bundle; a sixth of said bundles is positioned with an end face adjacent to the other end of the laminated face of said fourth bundle; a seventh of said bundles is positioned with a laminated face adjacent to an end face of said fifth and sixth bundles; an eighth of said bundles is positioned with a laminated face adjacent to a laminated face of said seventh bundle; and a ninth of said bundles is positioned with a laminated face adjacent to said laminated face of said eighth bundle, with a laminated face of said ninth bundle being positioned adjacent to an end face of said first bundle. 